We may try to treat set of extractelements as the shuffle wrongly if
they have different parents|types, are used in real gather tree entries
etc. Patch fixes this problem.
Because this is neither the gathering, not the vectorization, but something different. We should not gather instructions and should not vectorize them, just merge them as shuffle.
Because for this kind of tree entry we should not do anything - neither gather the items, nor mark them as vectorized, because instead we just merge them into a shuffle